<p>Let <i>B</i><sup><i>a,b</i></sup> be a weighted-fractional Brownian motion with Hurst indexes <i>a</i> and <i>b</i> such that <i>a</i> &gt; −1 and 0 ≼ <i>b</i> ≺ 1∧ (1 + <i>a</i>). In this paper, we consider the linear self-attracting diffusion <Equation ID="Equ1"> <MediaObject> <ImageObject Color="BlackWhite" FileRef="11425_2023_2261_Article_Equ1.gif" Format="GIF" Height="44" Rendition="HTML" Resolution="72" Type="Linedraw" Width="355" /> </MediaObject> <EquationSource Format="TEX">\(dX_{t}^{a,b}=dB_{t}^{a,b}-\theta \left(\int_{0}^{t}(X_{t}^{a,b}-X_{s}^{a,b})ds\right)dt+\nu dt\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mi>d</mi> <msubsup> <mi>X</mi> <mrow> <mi>t</mi> </mrow> <mrow> <mi>a</mi> <mo>,</mo> <mi>b</mi> </mrow> </msubsup> <mo>=</mo> <mi>d</mi> <msubsup> <mi>B</mi> <mrow> <mi>t</mi> </mrow> <mrow> <mi>a</mi> <mo>,</mo> <mi>b</mi> </mrow> </msubsup> <mo>−</mo> <mi>θ</mi> <mrow> <mo>(</mo> <msubsup> <mo>∫</mo> <mrow> <mn>0</mn> </mrow> <mrow> <mi>t</mi> </mrow> </msubsup> <mo stretchy="false">(</mo> <msubsup> <mi>X</mi> <mrow> <mi>t</mi> </mrow> <mrow> <mi>a</mi> <mo>,</mo> <mi>b</mi> </mrow> </msubsup> <mo>−</mo> <msubsup> <mi>X</mi> <mrow> <mi>s</mi> </mrow> <mrow> <mi>a</mi> <mo>,</mo> <mi>b</mi> </mrow> </msubsup> <mo stretchy="false">)</mo> <mi>d</mi> <mi>s</mi> <mo>)</mo> </mrow> <mi>d</mi> <mi>t</mi> <mo>+</mo> <mi>ν</mi> <mi>d</mi> <mi>t</mi> </math></EquationSource> </Equation> with <i>X</i><Stack> <sub>0</sub> <sup><i>a,b</i></sup> </Stack> = 0, where <i>θ</i> &gt; <i>0</i> and <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11425_2023_2261_Article_IEq1.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="43" /> </InlineMediaObject> <EquationSource Format="TEX">\(\nu \in \mathbb{R}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mi>ν</mi> <mo>∈</mo> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> </math></EquationSource> </InlineEquation> are two real parameters. The model is an analog of the linear self-interacting diffusion (see Cranston and Le Jan (1995)). Under the continuous observation, we study asymptotic behaviors of the least squares estimators <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11425_2023_2261_Article_IEq2.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(\hat{\theta}_{T}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <msub> <mrow> <mover> <mi>θ</mi> <mo stretchy="false">^</mo> </mover> </mrow> <mrow> <mi>T</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11425_2023_2261_Article_IEq3.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\(\hat{\nu}_{T}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <msub> <mrow> <mover> <mi>ν</mi> <mo stretchy="false">^</mo> </mover> </mrow> <mrow> <mi>T</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>. In particular, when <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11425_2023_2261_Article_IEq4.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="39" /> </InlineMediaObject> <EquationSource Format="TEX">\(b &gt;{1 \over 2}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mi>b</mi> <mo>&gt;</mo> <mrow> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> </mrow> </math></EquationSource> </InlineEquation> we obtain a new random variable <i>Z</i><Stack> <sub>1</sub> <sup><i>a,b</i></sup> </Stack> which is called the Rosenblatt random variable if <i>a</i> = 0, and we show that <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11425_2023_2261_Article_IEq5.gif" Format="GIF" Height="23" Rendition="HTML" Resolution="72" Type="Linedraw" Width="126" /> </InlineMediaObject> <EquationSource Format="TEX">\(C_{a,b}T^{2-2b}(\hat{\theta}_{T}-\theta)\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <msub> <mi>C</mi> <mrow> <mi>a</mi> <mo>,</mo> <mi>b</mi> </mrow> </msub> <msup> <mi>T</mi> <mrow> <mn>2</mn> <mo>−</mo> <mn>2</mn> <mi>b</mi> </mrow> </msup> <mo stretchy="false">(</mo> <msub> <mrow> <mover> <mi>θ</mi> <mo stretchy="false">^</mo> </mover> </mrow> <mrow> <mi>T</mi> </mrow> </msub> <mo>−</mo> <mi>θ</mi> <mo stretchy="false">)</mo> </math></EquationSource> </InlineEquation> converges in distribution to the sum of the chi-square random variable with i degree of freedom and the random variable <i>Z</i><Stack> <sub>1</sub> <sup><i>a,b</i></sup> </Stack>.</p>

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The linear self-attracting diffusion driven by the weighted-fractional Brownian motion II: The parameter estimation

  • Litan Yan,
  • Rui Guo,
  • Wenyi Pei

摘要

Let Ba,b be a weighted-fractional Brownian motion with Hurst indexes a and b such that a > −1 and 0 ≼ b ≺ 1∧ (1 + a). In this paper, we consider the linear self-attracting diffusion \(dX_{t}^{a,b}=dB_{t}^{a,b}-\theta \left(\int_{0}^{t}(X_{t}^{a,b}-X_{s}^{a,b})ds\right)dt+\nu dt\) d X t a , b = d B t a , b θ ( 0 t ( X t a , b X s a , b ) d s ) d t + ν d t with X 0 a,b = 0, where θ > 0 and \(\nu \in \mathbb{R}\) ν R are two real parameters. The model is an analog of the linear self-interacting diffusion (see Cranston and Le Jan (1995)). Under the continuous observation, we study asymptotic behaviors of the least squares estimators \(\hat{\theta}_{T}\) θ ^ T and \(\hat{\nu}_{T}\) ν ^ T . In particular, when \(b >{1 \over 2}\) b > 1 2 we obtain a new random variable Z 1 a,b which is called the Rosenblatt random variable if a = 0, and we show that \(C_{a,b}T^{2-2b}(\hat{\theta}_{T}-\theta)\) C a , b T 2 2 b ( θ ^ T θ ) converges in distribution to the sum of the chi-square random variable with i degree of freedom and the random variable Z 1 a,b .